In a multi-band radio terminal apparatus, even when communication frequency bands are switched, a reception intermediate frequency is selected to be equal to each other in the respective different communication frequency bands. As a result, the circuit arrangements of this multi-band radio terminal apparatus succeeding to the intermediate frequency signal circuit stage are commonly used in the respective communication frequency bands, and can be made simple. To this end, while a local oscillator signal is produced by a voltage-controlled oscillator, a phase-locked loop, and a doubler, in such a case that a communication is established within a plurality of communication frequency bands, the transmission/reception frequency intervals of which are different from each other, a mixer for a reception system and a mixer for a transmission system are commonly used so as to convert the frequency of the local oscillator signal into such a frequency existing between the communication frequency and the intermediate frequency.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A multi-band radio terminal apparatus comprising: a transmitter/receiver for processing radio communication signals of a plurality of communication frequency bands which include a first communication frequency band and a second communication frequency band, said radio communication signals being used to communicate with a base station; a first frequency converter for frequency-converting the frequency bands of said radio communication signals between the communication frequency bands and an intermediate frequency bands; a second frequency converter for converting said radio communication signals between base-band signals and an intermediate frequency signal; and a base-band signal processing circuit for handling a conversion between said base-band signals and audio signals, wherein said first frequency converter includes: one reception-sided mixer for converting a reception signal within the communication frequency band into another reception signal within the intermediate frequency band, said reception-sided mixer being commonly used for said first communication frequency band and said second communication frequency band by using a common intermediate frequency signal for said first communication frequency band and for said second communication frequency band, a second transmission-sided mixer for converting a transmission signal within the base- band signal from said base-band signal processing circuit into another transmission signal within the intermediate frequency band in such a manner that the intermediate frequency signal of said first communication frequency band is different from that of said second communication frequency band, a first transmission-sided mixer for converting a transmission signal within the intermediate frequency band into another transmission signal within the corresponding communication frequency band, and a first local oscillator for commonly supplying a first local oscillator signal to both said reception-sided mixer and said first transmission-sided mixer, a second local oscillator for supplying local oscillator signals for said first communication frequency band and said second communication frequency band to said second transmission-sided mixer, and wherein said first local oscillator includes: an oscillator, a switch, and a frequency doubling circuit for selectively supplying a frequency of said oscillator output and a frequency obtained by doubling said oscillator output in response to the frequency band of the radio signal used in the communication between the base station and the multi-band radio terminal apparatus.
2. A multi-band radio terminal apparatus as claimed in claim 1 , wherein said base-band signal processing circuit includes a controller, and a local oscillator frequency of said second local oscillator is controlled by said controller.
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March 3, 1999
August 20, 2002
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